High basal level gene expression of thymidine phosphorylase (platelet-derived endothelial cell growth factor) in colorectal tumors is associated with nonresponse to 5-fluorouracil

The gene expression levels of the nucleoside cleavage enzyme/angiogenic factor thymidine phosphorylase (TP), also known as platelet-derived endothelial cell growth factor, were measured by quantitative reverse transcription-PCR in 38 pretreatment biopsies of colorectal tumors from patients who were...

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Published in:Clinical cancer research 1998-10, Vol.4 (10), p.2371-2376
Main Authors: METZGER, R, DANENBERG, K, LEICHMAN, C. G, SALONGA, D, SCHWARTZ, E. L, WADLER, S, LENZ, H.-J, GROSHEN, S, LEICHMAN, L, DANENBERG, P. V
Format: Article
Language:English
Subjects:
Antimetabolites, Antineoplastic - therapeutic use
Antineoplastic agents
Biological and medical sciences
Camptothecin - analogs & derivatives
Camptothecin - therapeutic use
Chemotherapy
Colorectal Neoplasms - drug therapy
Colorectal Neoplasms - metabolism
Fluorouracil - therapeutic use
Humans
Medical sciences
Pharmacology. Drug treatments
RNA, Messenger - analysis
Thymidine Phosphorylase - genetics
Thymidylate Synthase - genetics
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Summary:The gene expression levels of the nucleoside cleavage enzyme/angiogenic factor thymidine phosphorylase (TP), also known as platelet-derived endothelial cell growth factor, were measured by quantitative reverse transcription-PCR in 38 pretreatment biopsies of colorectal tumors from patients who were subsequently treated with 5-fluorouracil (5-FUra) and leucovorin (LV). The range of TP gene expression (relative mRNA levels) in those tumors nonresponsive to 5-FUra was much broader than that of the responding tumors. In contrast to in vitro studies that had shown that an increased intracellular level of TP potentiates the activity of 5-FUra by converting it to the more cytotoxic nucleoside form 5-fluoro-2'deoxyuridine, tumors with the highest basal TP expressions were nonresponders to 5-FUra/LV therapy. The mean TP mRNA level in the nonresponding tumors was 2.6-fold higher than that of the responding patients. We had shown previously that high expression of thymidylate synthase (TS), the target enzyme of 5-FUra, was also a predictor of nonresponse to 5-FUra (L. Leichman et al, J. Clin. Oncol., 15: 3223-3229, 1997). TP and TS expressions were found to be independent variables in these tumors, so that low expression levels of both TS and TP in tumors predicted a very high response rate (11 of 14) to 5-FUra/LV as well as a significantly longer survival, whereas none (0 of 24) of the patients with high expression of either TP or TS were responders.
ISSN:1078-0432
1557-3265